Reduced Graphene Oxide Nanosheets Decorated with Au Nanoparticles as an Effective Bactericide: Investigation of Biocompatibility and Leakage of Sugars and Proteins

This article reports the synthesis of a composite of reduced graphene oxide nanosheets decorated with gold nanoparticles (AuNPs-rGO) through an ecofriendly route, and the investigation of its biocompatibility to HeLa cells and its antibacterial activity against Gram-positive and Gram-negative bacteria. The composite material is synthesized by using an environmentally friendly reducing agent, ascorbic acid, under ultrasonication. The composite material is characterized by UV/Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis (TGA). HRTEM analysis reveals the formation of spherical Au NPs of 8-45nm in size on the folded rGO nanosheets, which is further confirmed by XRD and SAXS analyses. The AuNPs-rGO shows good biocompatibility with cervix carcinoma, human (HeLa) cells, and possesses high antibacterial activity against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonous aeruginosa). The bacterial cell death is caused by the leakage of sugars and proteins from the cell membrane in contact with the AuNPs-rGO composite material.